1. Field of the Invention
The present invention relates to a vehicle driving force control device that improves occupants' comfort in a vehicle provided with an engine and an automatic transmission having fixed gears ratios.
2. Description of the Related Art
In a vehicle provided with an engine and an automatic transmission having fixed gear ratios, when a throttle valve and an acceleration pedal, which adjust output of the engine, are connected mechanically through a wire, or the like, an accelerator operation amount, which is an amount by which the acceleration pedal is depressed, is in one-to-one correspondence with an opening degree of the throttle valve (throttle valve opening degree). The above one-to-one correspondence basically also applies to an electronic throttle valve in which the throttle valve is electrically interlocked with the accelerator pedal. However, in a vehicle having the electronic throttle valve, some vehicle driving force control devices temporarily execute electronic throttle control that does not follow a throttle valve reference characteristic, which is a predetermined relationship between an accelerator operation amount and a throttle opening degree. For example, Japanese Patent No. 2929396 describes one of the above described vehicle driving force control devices. In this vehicle driving force control device, in order to avoid frequent gear shift in an automatic transmission having fixed gear ratios, when a necessary driving force that will be obtained through gear shift according to a predetermined shift pattern (shift line map) can be output by adjusting the throttle valve opening degree without that gear shift, the gear shift is not performed and the throttle valve opening degree is adjusted to obtain the necessary driving force irrespective of the throttle valve reference characteristic.
However, the vehicle driving force control device of Japanese Patent No. 2929396 executes adjustment of the throttle valve opening degree in order to avoid frequent gear shift in the automatic transmission having fixed gear ratios, that is, in order to avoid gear shift. Thus, when shift control is actually executed, the shift control is executed as usual. Thus, in the vehicle driving force control device of the Japanese Patent No. 2929396, when the shift control of the automatic transmission is executed, the driving force inevitably varies in a stepped manner.